Coding method of dividing information block serving as conversion unit into a plurality of sub-blocks to perform coding for each sub-block, and coding apparatus

Abstract

The information block that is sequentially extracted from an information sequence and that serves as a conversion unit is divided into a plurality of sub-blocks, Then, counting is performed of the information items number of at least one of "0" and "1" that is contained in each sub-block for each sub-block of a plurality of the thus-divided sub-blocks. Then, there is performed, according to the counted result that has been thus obtained, inversion yes/no determination of whether the original information contained in each sub-block should be inverted under the consideration of minimizing the difference between the number of codes "0", and the number of codes "1", contained in the code block as a whole. Then, there is performed, regarding the sub-block, with respect to which a determination of that the original information should be inverted has been made, coding of inverting the original information contained in this sub-block and there is added, with respect to this sub-block, an inversion identification code that represents the effect that the original information has been inverted, while, regarding the sub-block, with respect to which a determination of that the original information should not be inverted has been made, there is performed coding of leaving intact the original information contained in this sub-block without inverting the same and, with respect to this sub-block there is added a maintenance identification code that represents the effect that the original information has been left intact. And by unifying a plurality of code sub-blocks, each of which has had either one of the inversion identification code or maintenance identification code added thereto, the information block is converted into a code block.

What is claimed is: 
     
       1. A coding method which is used when converting an information block that is sequentially extracted from an information sequence and that serves as a conversion unit into a code block one by one, the coding method comprising the steps of: dividing the information block into a plurality of sub-blocks;   counting the information items number of at least one of "0" and "1" that is contained in each sub-block for each sub-block;   performing, according to the counted result that has been obtained for each sub-block, inversion yes/no determination about whether or not the original information contained in each sub-block should be inverted for each sub-block under the consideration of minimizing the difference between the number of codes "0", and the number of codes "1", contained in the code block as a whole;   performing, regarding the sub-block, with respect to which a determination of that the original information should be inverted has been made as a result of this inversion yes/no determination, coding of inverting the original information contained in this sub-block and adding, with respect to the code sub-block that has had the original information inverted, an inversion identification code that represents the effect that the original information has been inverted, while, regarding the sub-block, with respect to which a determination of that the original information should not be inverted has been made, performing coding of leaving intact the original information contained in this sub-block without inverting the same and, with respect to the code sub-block that has had the original information maintained as is, adding a maintenance identification code that represents the effect that the original information has been left intact; and   unifying a plurality of code sub-blocks, each of which has had either one of the inversion identification code and maintenance identification code added thereto, thereby converting the information block into a code block.   
     
     
       2. A coding method according to claim 1, wherein each of the inversion identification code and the maintenance identification code has a one-code length. 
     
     
       3. A coding method according to claim 1, wherein the information block is divided so that the original information bit lengths of the plurality of the divided sub-blocks obtained by the division are equal to one another. 
     
     
       4. A coding method according to claim 1, wherein in the inversion yes/no determination step,   according to the counted result that has been obtained for each sub-block, it is determined whether the original information contained in each sub-block should be inverted for each sub-block under the consideration of minimizing the difference between the number of codes "0", and the number of codes "1", contained in the code block as a whole and under the consideration that, in a case where there is a difference between the number of the codes "0" and the number of the codes "1" contained in the code block, one of "0" and "1" be the majority.   
     
     
       5. A coding method according to claim 4, wherein when the coding procedure of the information blocks each serving as the conversion unit has been performed over a plurality of the conversion units, the inversion yes/no determination, that is based on the consideration of that the codes "1" contained in the code block become the majority, and the inversion yes/no determination, that is based on the consideration of that the codes "0" contained in the code block become the majority, are performed respectively in consideration of that the frequencies with which to perform the respective determinations be substantially in equilibrium with each other as a whole.   
     
     
       6. A coding method according to claim 5, wherein no inconvenience occurs even when either of the inversion yes/no determination, that is based on the consideration of that the codes "1" contained in the code block become the majority, and the inversion yes/no determination, that is based on the consideration of that the codes "0" contained in the code block become the majority, is performed successively.   
     
     
       7. A coding apparatus which has been constructed so as to convert an information block that is sequentially extracted from an information sequence and that serves as a conversion unit into a code block one by one, the coding apparatus comprising: dividing means for dividing the information block into a plurality of sub-blocks;   a plurality of counting means for counting the information items number of at least one of "0" and "1" that is contained in each sub-block for each sub-block;   inversion yes/no determination means for performing, according to the counted result that has been obtained for each sub-block by counting performed in a plurality of the counting means, inversion yes/no determination of whether the original information contained in each sub-block should be inverted for each sub-block under the consideration of minimizing the difference between the number of codes "0", and the number of codes "1", contained in the code block as a whole;   maintenance/inversion coding means for performing, regarding the sub-block, with respect to which a determination of that the original information should be inverted has been made as a result of this inversion yes/no determination performed in the inversion yes/no determination means, coding of inverting the original information contained in this sub-block while, regarding the sub-block, with respect to which a determination of that the original information should not be inverted has been made, performing coding of leaving intact the original information contained in this sub-block without inverting the same; and   adding and unifying means for adding, with respect to the code sub-block on which coding of inverting the original information has been performed in the maintenance/inversion coding means, an inversion identification code that represents the effect that the original information has been inverted, while, with respect to the code sub-block on which coding of maintaining the original information as it is without inverting the same has been performed in the maintenance/inversion coding means, adding a maintenance identification code that represents the effect that the original information has been left intact, and for unifying a plurality of code sub-blocks, each of which has had one of the inversion identification code and maintenance identification code added thereto.   
     
     
       8. A coding apparatus according to claim 7, wherein each of the inversion identification code and the maintenance identification code has a one-code length. 
     
     
       9. A coding apparatus according to claim 7, wherein the dividing means divides the information block into a plurality of sub-blocks so that the original information bit lengths of a plurality of the divided sub-blocks that are obtained by division are equal to one another. 
     
     
       10. A coding apparatus according to claim 7, wherein the inversion yes/no determination means performs, according to the counted result that has been obtained for each sub-block by counting performed in a plurality of the counting means, a determination about whether or not the original information contained in each sub-block should be inverted for each sub-block under the consideration of minimizing the difference between the number of codes "0", and the number of codes "1", contained in the code block as a whole and under the consideration that, in a case where there is the difference between the number of the codes "0" and the number of the codes "1" contained in the code block, one of "0" and "1" be the majority.   
     
     
       11. A coding apparatus according to claim 10, wherein when the coding procedure of the information blocks each serving as a conversion unit has been performed over a plurality of the conversion units, the inversion yes/no determination performed in the inversion yes/no determination means, that is based on the consideration of that the codes "1" contained in the code block become the majority, and the inversion yes/no determination performed therein, that is based on the consideration of that the codes "0" contained in the code block become the majority, are performed respectively in consideration of that the frequencies with which to perform the respective determinations be substantially in equilibrium with each other as a whole.   
     
     
       12. A coding apparatus according to claim 11, wherein no inconvenience occurs even when either of the inversion yes/no determination performed in the inversion yes/no determination means, that is based on the consideration of that the codes "1" contained in the code block become the majority, and the inversion yes/no determination performed therein, that is based on the consideration of that the codes "0" contained in the code block become the majority, is performed successively.